/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.LinkedHashMap;
import java.util.concurrent.atomic.AtomicInteger;

import com.google.common.annotations.GwtCompatible;

/**
 * A {@code Multiset} implementation with predictable iteration order. Its
 * iterator orders elements according to when the first occurrence of the
 * element was added. When the multiset contains multiple instances of an
 * element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to
 * the multiset, the element will appear at the end of the iteration.
 * 
 * @author Kevin Bourrillion
 * @author Jared Levy
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
@GwtCompatible(serializable = true)
// we're overriding default serialization
public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> {

    /**
     * Creates a new, empty {@code LinkedHashMultiset} using the default initial
     * capacity.
     */
    public static <E> LinkedHashMultiset<E> create() {
        return new LinkedHashMultiset<E>();
    }

    /**
     * Creates a new, empty {@code LinkedHashMultiset} with the specified
     * expected number of distinct elements.
     * 
     * @param distinctElements
     *            the expected number of distinct elements
     * @throws IllegalArgumentException
     *             if {@code distinctElements} is negative
     */
    public static <E> LinkedHashMultiset<E> create(int distinctElements) {
        return new LinkedHashMultiset<E>(distinctElements);
    }

    /**
     * Creates a new {@code LinkedHashMultiset} containing the specified
     * elements.
     * 
     * @param elements
     *            the elements that the multiset should contain
     */
    public static <E> LinkedHashMultiset<E> create(
            Iterable<? extends E> elements) {
        LinkedHashMultiset<E> multiset = create(Multisets
                .inferDistinctElements(elements));
        Iterables.addAll(multiset, elements);
        return multiset;
    }

    private LinkedHashMultiset() {
        super(new LinkedHashMap<E, AtomicInteger>());
    }

    private LinkedHashMultiset(int distinctElements) {
        // Could use newLinkedHashMapWithExpectedSize() if it existed
        super(new LinkedHashMap<E, AtomicInteger>(
                Maps.capacity(distinctElements)));
    }

    /**
     * @serialData the number of distinct elements, the first element, its
     *             count, the second element, its count, and so on
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        Serialization.writeMultiset(this, stream);
    }

    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        int distinctElements = Serialization.readCount(stream);
        setBackingMap(new LinkedHashMap<E, AtomicInteger>(
                Maps.capacity(distinctElements)));
        Serialization.populateMultiset(this, stream, distinctElements);
    }

    private static final long serialVersionUID = 0;
}
